Attention deficit hyperactivity disorder is a medical condition that affects more than 15 million Americans. Its symptoms — including distractibility, impulsivity and hyperactivity — can seriously interfere with a person's ability to function from day to day. With the right support and treatment, children and adults with ADHD often lead successful lives.

Plenty of ADHD naysayers, however, don't recognize the condition. Become an activist, just in time for ADHD Awareness Day on September 20, and the next time you encounter a skeptic, provide him or her with some fast facts. Below is the truth about ADHD — use it to dispel common myths and misconceptions.

ADHD is a real medical disorder.
It has been recognized as a legitimate diagnosis by major medical, psychological and educational organizations, including the National Institutes of Health, the American Psychiatric Society and the U.S. Department of Education.

ADHD is biologically based. Research shows that it's the result of an imbalance of chemical messengers, or neurotransmitters, within the brain. Its primary symptoms are inattention, impulsiveness and, sometimes, hyperactivity. People with ADHD have a great deal of difficulty with some aspects of daily life, including time management and organization.